This application is a national stage application, according to Chapter I of the Patent Cooperation Treaty. This application claims the priority date of Jan. 10, 2000 for Great Britain Patent Application No. 0000331.9.
This invention relates to the field of orthopaedic medicine and more specifically to an improved medical bandage formed of a moisture curable resin and a flexible permeable substrate, a method of manufacture of such a medical bandaging product, and a bandaging system comprising such a bandage within a moisture impervious package with means for resealing the package against entry of moisture.
Medical bandages for use in the treatment of injuries, such as broken bones requiring immobilisation of a body part, are generally formed from a strip of fabric or scrim material impregnated with a substance that hardens into a rigid structure after the strip has been wrapped around the body member. The hardening substance traditionally used in carrying out this procedure is Plaster of Paris.
Conventional practice has been to fabricate or splint upon an injured limb by initially applying to the limb a protective covering of a cotton fabric or the like and then overwrapping the covering and limb with a woven cloth impregnated with Plaster of Paris which has been wetted by dipping in water immediately prior to application. This is still in widespread use but possesses several significant disadvantages. For example, the above described application procedure is messy and time consuming. Several components are required and considerable skill is necessary.
In order to alleviate the above-recited disadvantages of the application procedure for Plaster of Paris casts and splints, unitary splinting materials have been devised and are disclosed in, for example, U.S. Pat. Nos. 3,900,024, 3,923,049 and 4,235,228.
All of these patents describe a padding material with a plurality of layers of Plaster of Paris impregnated cloth.
Such unitary splinting materials are not as messy and can be applied more quickly but still suffer from a number of disadvantages inherent in Plaster of Paris materials.
All Plaster of Paris splints have a relatively low strength to weight ratio, which results in a finished splint that is very heavy and bulky.
Plaster of Paris splints are slow to harden, requiring 24 to 72 hours to reach maximum strength. Since Plaster of Paris breaks down in water, bathing and showering are difficult.
Even if wetting due to these causes can be avoided, perspiration over an extended period can break down the Plaster of Paris and create a significant problem with odour and itching.
A significant advance in the art of casting and splinting is disclosed in U.S. Pat. Nos. 4,411,262 and 4,502,479.
The casting materials disclosed in these patents comprise a flexible fabric impregnated with a moisture curing resin enclosed in a moisture free, moisture impervious package.
Compared to Plaster of Paris, these products are extremely lightweight, have a very high strength to weight ratio and can be made relatively porous, permitting a flow of air through the casting material.
Prior art moisture curing systems included a package within which is contained a plurality of layers of fabric, such as fibreglass, impregnated with a moisture curing resin.
No provision is made for re-closing the package, so that the entire material must be very quickly used after removal from the package since such moisture curing resins will cure in a relatively short period due merely to contact with atmospheric moisture.
This technology has permitted the development of lightweight, easy to apply splints, as exemplified in U.S. Pat. Nos. 4,770,299, 4,869,049, 4,899,738, 5,003,970 and 5,415,622. Such splints now dominate the market for medical splints.
However, known fabrics have the disadvantage that, if the fabric, e.g. fibreglass, is cut this may leave cut fibres and yarns projecting from the splinting material.
As manufactured, this fabric is relatively soft and flexible, and has relatively good conformability. Moreover, the substrate is fully enclosed with the surrounding padding material.
After curing, however, the cut fibres and yarns become hard and needle-like. These projections can project through the thickness of the padding material into contact with the skin of the patient causing skin-sticks, cuts, irritation and itching.
Moreover, the splinting manufacturing process utilising flat fabric is relatively labour intensive since the fabric must be overlaid with other layers of fabric, usually 4 to 8, to produce the substrate. In order to properly form the substrate, the overlaid layers must be carefully aligned so that the width and thickness are even.
In instances where the multiple overlaid layers are stitched together, even more labour is required. Such multi-layered fabrics tend to be bulky and may require a high proportion of resin, further adding to the weight of the finished product. Several layers can mean the product is difficult to handle, whereby each additional layer may reduce flexibility.
Most fabrics used for the substrates of casting and splinting materials are knitted fabrics, as these are inexpensive and readily available. However, knitted fabrics have the disadvantage that there may be limited width-ways conformability
Knitted products may also suffer from the disadvantage of having limited torsional stiffness and directionally specific properties, which can be important for the treatment of specific injuries.
Linear fabrics of knitted orthopaedic products often require a relatively large amount of hardening agent, typically 40% by weight of the total weight.
From the above discussion, it can be seen that both the conventional Plaster of Paris casting method and the more recent moisture curable resin casting method possess both advantages and disadvantages.
On the one hand, Plaster of Paris casts are bulky, heavy and difficult to apply whereas moisture curable resin casts are lightweight, durable and relatively easy to apply.
Plaster of Paris can be very easily stored and used as needed since it has a relatively long shelf life so long as it is not completely wetted.
On the other hand, the moisture curable resins are very sensitive to the presence of even minute amounts of moisture, which requires that either the material be packaged in a wide variety of different shapes and sizes or unused portions be discarded, generating a substantial amount of waste and increasing the effective cost of the product.
Therefore, it is an object of the present invention to provide a bandaging product that has a substrate that is uniform in dimension without the requirement for additional fabrication steps after formation of the substrate.
It is an object of the invention to provide a bandaging product that has a braided or tubular substrate that does not require additional layers for strength.
It is an object of the invention to provide a bandaging product that utilises a tubular braided fabric structure as a bandaging substrate.
It is also an object of the invention to provide a bandaging product that combines the advantages of both Plaster of Paris and moisture curable resin systems while avoiding their respective disadvantages.
Thus, according to a first aspect of the present invention there is provided a medical bandaging product having a moisture curable hardening agent and a flexible liquid-permeable substrate wherein the flexible liquid permeable substrate is a braided and/or tubular fabric.
In one embodiment, the substrate will carry the hardening agent in and/or on its structure, ready for easy curing and application.
Surprisingly it has been found that the use of a braided and/or tubular fabric for the flexible permeable substrate of a bandaging product gave a product that prior to curing or hardening is easy to handle with good conformability but which after curing gives a rigid strong orthopaedic product.
This gives an orthopaedic product, such as a casting or splinting product that is stronger and wears better against abrasions, than the casts of the prior art for similar weight of products. The bandaging products of the present invention therefore have a longer useful life as an orthopaedic cast or splint.
Having a stronger cast as described by the present invention also allows less hardening agent to be used to cure and harden the bandaging product, thus being cheaper and easier to manufacture.
Using less hardening agent and layers of fabric for a bandaging product as described in the present invention also gives a lighter product that may still have the required strength needed for an orthopaedic cast or splint.
Having less hardening agent to cure also gives a reduced exotherm, the heat produced on curing which may be uncomfortable to the user.
In one embodiment, the substrate will be braided.
It has surprisingly been found that the braided and/or tubular structure has enhanced physical properties including added strength and enhanced torsional rigidity.
According to a second aspect of the present invention there is provided a method of manufacture of a medical bandaging product carrying a moisture curable agent comprising the step of applying a moisture curable agent to a braided and/or tubular substrate. In one embodiment, the substrate will be braided.
The last object of the invention (to provide a bandaging product that combines the advantages of both Plaster of Paris and moisture curable resin systems while avoiding their respective disadvantages) is accomplished by providing a unitary splinting system with improved strength and convenience.
Thus, in a third aspect of the present invention there is provided a bandaging system comprising a bandaging product comprising a moisture curable agent in and/or on a substrate within a moisture impervious package with means for resealing the package against entry of moisture after a desired length of bandaging product has been removed for use.
In this manner, hardening of the bandaging product remaining in the moisture impervious package is prevented thereby increasing the cost effectiveness of the system.
In one embodiment of the third aspect of the present invention there is provided a bandaging system comprising a bandaging product comprising a moisture curable agent in and/or on a substrate that is braided and/or tubular.
The braided and/or tubular fabric of the substrate comprised in a bandaging product may be provided in several significantly advantageous embodiments. For example, it may be a non-tubular braid, e.g. a webbing strap, formed as a length of flat braided material.
It may alternatively be a tube seamed from a length of flat material that is looped around and suitably attached to form a tubular structure of the present invention, preferably with the raw ends of the flat positioned on the inside of the tube.
The material that is looped around and suitably attached to form a tubular structure of the present invention may be braided.
The braided and/or tubular fabric of the substrate comprised in a bandaging product may be made of any suitable fibres or yarns or combinations thereof.
Suitable fibres include polyester fibres, carbon fibres and jute although any natural or synthetic fibre that can be spun into a suitable yarn or monofilament material and braided may be used.
It is envisaged that in a preferred embodiment that the braided and/or tubular fabric will contain glass fibres.
Resilient fibre such as elastomers e.g. polypropylene fibres can also be used, whether alone or in combination with other fibres, to enhance to give desired properties such as extensibility and impact resistance.
The structure of the braided and/or tubular substrate may be initially manufactured as a braided and/or tubular structure or may first be manufactured as a flat, optionally braided material that is looped around and suitably attached to form the braided and/or tubular structure of the present invention.
Preferably, the braided and/or tubular substrate is manufactured initially as a braided and/or tubular structure ready for use in the present invention, e.g. formed of a suitable fibre such as fibreglass into a webbing strap, formed as a length of flat braided material on a braiding machine, or into length of braided tube on a circular braiding machine.
Embodiments of the present invention may have the fibres nominally at +/xe2x88x9245 degrees to each other thus offering excellent torsional rigidity.
The angle of the fibres of the braid may vary, offering a wide range of different torsional rigidity properties.
The stretch of the material, whether width ways or lengthways will vary the angle of the fibres relative to each other.
It is envisaged that when the braided and/or tubular substrate is stretched lengthways the fibres will run along the lengthways direction at a smaller angle from the lengthways axis then when the braided and/or tubular substrate is stretched widthways.
When the angle of the fibres running lengthways is small when measured from the lengthways axis the substrate has greater lengthways strength than when the angle is large.
Likewise, when the angle of the fibre running widthways is small when measured from the widthways axis the substrate has greater widthways strength than when the angle is small.
Further variations of torsional rigidity may be possible by the inclusion of unidirectional fibres.
These fibres can be laid lengthways or widthways depending on the desired effect required. Such fibres may be elastic fibres.
In short, it is the fibre orientation that gives different structural properties, for instance torsional rigidity, to the braided and/or tubular substrate.
The present invention allows easy changing of the fibre orientation thus enabling a wide range of different rigidity properties of the substrate.
The moisture curable hardening agent used with the bandage of the present invention may be any suitable agent that when cured hardens the bandage to form the orthopaedic support product. A number of commercially available hardening agents are widely available including Plaster of Paris and synthetic resins.
Suitable hardening agents include water curable synthetic resins for casting or splinting products, such as urethane resins formed from the reaction of a polyol with an excess of polyisocyanate (as disclosed in patent applications GB 2092606 A and WO 86/01397). Other suitable agents include an alkoxy silane terminated prepolymer (disclosed in WO96/23531) or an acrylic terminated prepolymer.
These are stronger and wear better against abrasions, than the casts from similar weight products.
The hardening agent may be applied separately to the substrate prior to curing, or the substrate may carry the hardening agent. In a preferred embodiment, the substrate will carry the hardening agent ready for easy curing and application.
Having a bandaging product whereby the substrate carries the hardening agent helps ensure even distribution of the hardening agent throughout the substrate.
Suitably the hardening agent will be coated evenly on the substrate and may typically have a hardening agent coating of around 20% of the total weight of the product.
The braided and/or tubular structure also enables the finished product to have a variety of different thicknesses. In different circumstances a thick, or thin, bandage may be required and the braided and/or tubular structure may be shaped accordingly.
The thickness of the structure may offer different strength and stiffness properties, which according to what is required the appropriate thickness can be chosen.
Suitable a methods of applying a moisture curable agent to a braided and/or tubular substrate include conventional methods of applying a moisture curable agent to a similar substrate for casting or splinting products, such as nip coating and impregnation.
In one embodiment, the substrate will be braided and such methods of applying a moisture curable agent to a braided and/or tubular substrate include conventional methods for casting or splinting products, such as nip coating and impregnation.
In use the braided and/or tubular substrate may, optionally, be pulled over a core of, for example, foam or COREMAT(trademark), (COREMAT is a Trade Mark of British Vita) to give extra strength or stiffness to the structure.
Different sized cores may be used to give a product of various strengths and stiffness as well as thickness.
The core may be supplied in place, within the braided and/or tubular braid and ready for use, or may be supplied separately.
In embodiments where a core is to be used, the width of core may be predetermined in order to determine the correct stretch required of the braided and/or tubular bandage to have the desired torsional rigidity property. Different predetermined widths of core may be used for different torsional rigidity properties.
Different braids, or different designs of braids, may be used to give different properties to the braided and/or tubular structure.
For instance, if enhanced properties are required along the length of the product, unidirectional fibres can be laid down. If the torsional properties are less important, a wider braid can be used and pulled to bring the fibres closer to unidirectional.
It is envisaged that the bandaging product of the present invention will be suitably stored in a container prior to use.
The container used to store the bandaging product of the present invention may be made from any tough durable tear resistant material that will not tear or rip during rough handling, but preferably which can be easily opened by hand. Preferably, this material should be impervious to liquid and gas.
Such materials may be metallic foil or plastics e.g. polyethylene or the like, or laminates thereof.
In the third aspect of the present invention, the container protecting the bandaging product will be resealable so that the entire bandaging product is not required to be used at once.
A suitable resealing means will be employed to reseal the container of the bandaging product.
The container protecting the bandaging product will often comprise a moisture free, moisture impervious package that is resealable, so that the entire bandaging product is not required to be used at once.
Suitable materials and properties for the resealable container protecting the bandaging product will be as described by way of example only with reference to a general container protecting the bandaging product above.
As described, it may be of metallic foil or plastics e.g. polyethylene or the like, or laminates thereof.
By way of example only, the container protecting the bandaging product will often comprise a moisture free, moisture impervious enlarged product storage package, which is integral and communicates with one end of a dispensing sleeve, through which the medical bandaging product in the container is dispensed.
A coil of the medical bandaging product is positioned in the package and the elongate dispensing sleeve may fit snugly around the running end of the medical bandaging product.
The farther end of the dispensing sleeve is openable, but resealable, so that the entire bandaging product is not required to be used at once.
The medical bandaging product may be coiled into a relatively tight coil that limits exposure to air of the medical bandaging product remaining in the container.
The snug fit of the elongate dispensing sleeve around the running end of the medical bandaging product also limits exposure to air of the medical bandaging product remaining in the container.
When the end is properly sealed, the container is sufficiently airtight so that the medical bandaging product remains in its soft, uncured state for much longer that the usual length of time needed to exhaust the supply of medical bandaging product in the container.
If a short length of the medical bandaging product adjacent to the opening should happen to harden, it can be cut away and discarded.
A suitable resealing means will be employed to reseal the interior of container securely against intrusion of moisture, e.g. heat-sealing, or a clamp of any suitable type, such as a scissors type clamp.
Other types of sealing mechanisms are possible such as, for example, a soft, conformable gasket device with spring loaded compression, or a xe2x80x9czip-lockxe2x80x9d type integrally formed zipper of a type typical on sandwich bags and other food storage bags, moisture proof tape, or a screw action of sufficient strength to prevent entry of moisture into the sleeve.
One particular suitable device is a pair of spring loaded rollers which as compression takes place rolls slightly backwards, pushing the medical bandaging product back slightly into the sleeve to permit a better seal.